Reduction of methyl isothiocyanate atmospheric emissions after application of metam sodium by shank injection.

Abstract

Regulatory initiatives in the United States have created the impetus to reassess application methods for metam sodium (sodium -methyldithiocarbamate), a methyl isothiocyanate (MITC) generator, to reduce flux to the atmosphere. This paper compares flux rates in the years 1990 through 2002 with flux rates based on four studies conducted during the period 2008 through 2010 in California, Michigan, Wisconsin, and Washington using current shank-injection/compaction methods. Up to a 100-fold reduction in peak flux rates and total loss of MITC have been observed. A combination of the following factors led to these reductions in flux: soil moisture goals set at 70% of the field water holding capacity; improved design of shank-injection systems to break up the voids after injection; effective shank compaction to further reduce volatilization; and the use of water sealing, where applicable. These refinements in the application methods for metam sodium provide a means to merge environmental and agricultural goals in the United States and in other countries that use metam sodium. This paper documents the reduced atmospheric emissions of MITC under commercial production conditions when applied using good agricultural practices. This research also shows that MITC flux can be effectively managed without the use of high barrier tarp material.